1. Field of the Invention
This invention is directed to the field of providing commutation control of inductive loads, and in particular, circuitry for use in controlling multi-pole DC brushless motors.
2. Background Art
There are many applications which require the control of current in inductive loads where the current must be switched (commutated) from one value to another value or from one inductive load to another load. When the current through an inductor is reduced rapidly, a reverse voltage is generated that is proportional to the rate of the current change (di/dt). If the current passing through an inductive load is abruptly interrupted, the voltage generated by the inductor can be of sufficient magnitude to damage other components. Even if the transient is not destructive to other components, it may generate undesirable electromagnetic interference (EMI) which can interfere with the operation of adjacent electronic circuits.
It is therefore desirable to control these transients in such situations. Prior art has employed special networks attached to the inductive load to suppress or reduce the transients. In the past, such devices as flyback diodes or varistors have been used to suppress transients and capacitor or resistor-capacitor networks have been employed to reduce transients.